Blog Posts in March 2016

How Hard Is It to Think about Failures?

Mr. A. Anonymous, frequent contributor to my blog posts left this bit of wisdom comment on the VMware NSX Update blog post:

I don't understand the statement that "whole NSX domain remains a single failure domain" because the 3 NSX controllers are deployed in the site with primary NSX manager.

I admit I was a bit imprecise (wasn’t the first time), but is it really that hard to ask oneself “what happens if the DCI link fails?

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x86-Based Switching at Ludicrous Speed on Software Gone Wild

Imagine you want to have an IPv6-only access network and transport residual IPv4 traffic tunneled across it. Sounds great, but you need to terminate those tunnels and encapsulate/decapsulate IPv4 traffic at multi-gigabit rate.

There are plenty of reassuringly-expensive hardware solutions that can do that, or you could work with really smart people and get software-based solution that can do 20 Gbps per CPU core.

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Table Sizes in OpenFlow Switches

This article was initially sent to my SDN mailing list. To register for SDN tips, updates, and special offers, click here.

Usman asked a few questions in his comment on my blog, including:

At the moment, local RIB gets downloaded to FIB and we get packet forwarding on a router. If we start evaluating too many fields (PBR) and (assume) are able to push these policies to the FIB - what would become of the FIB table size?

Short answer: It would explode ;)

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How Realistic Is High-Density Virtualization?

A while ago I guestimated that most private clouds don’t have more than a few thousand VMs, and that they don’t need more bandwidth than what two ToR switches could provide.

Last autumn Iwan Rahabok published a blog post describing the compute- and storage parts of it, and I had a presentation describing the networking aspects of high-density consolidation. However…

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Data Center Fabrics and SDN

A few days ago Inside-IT published an interview Christoph Jaggi did with me. In case you don’t understand German, here’s the English version of it.

There is a lot of talk about data center fabrics. What problem do they try to solve?

The data center fabrics are supposed to solve a simple-to-define problem: building a unified data center infrastructure that seamlessly supports data and storage communications. As always, the devil hides in the details.

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You Want Your Network to Be like Google’s? Really?

This article was initially sent to my SDN mailing list. To register for SDN tips, updates, and special offers, click here.

During one of my SDN workshops one of the attendees working for a mid-sized European ISP asked me this question:

Our management tells us we should build our network like Google does, including building our own switches. Where should we start?

The only answer I could give him was “You don’t have a chance.

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